Coastal wetland resilience to climate variability: A hydrologic perspective

Climate-induced disturbances are expected to increase in frequency and intensity and affect wetland ecology by altering its hydrology. Investigating how wetland hydrology responds to climate disturbances is an important first step to understand the ecological response of coastal wetlands to these disturbances. Wetland hydrologic resilience, the ability of wetland in absorbing disturbances and restoring to pre-disturbance conditions in hydrological function, is a critical measure of wetland hydrological response to climate disturbances. However, a practical methodology for quantifying wetland hydrologic resilience (HR) is still lacking. This study aimed to improve the approach for quantifying the hydrologic resilience of wetland ecosystems to climate variability and climate change. A set of quantitative metrics was developed including the variations of groundwater table, overland flow, and saltwater table. This approach was then applied to a coastal landscape that includes coastal-forested and herbaceous wetlands in North Carolina, USA. We investigated the threshold behaviors of groundwater table, overland flow, and saltwater table for a 20-year period (1995-2014) by applying a regional scale wetland hydrological model, Penn State Integrated Hydrological Model for wetland hydrology (PIHM-Wetland). We found that the multiscale variations of groundwater table under dry climatic conditions is a good indicator of wetland HR to drought. The variation of overland flow during rainfall events effectively quantified HR to wet periods. We also found that the variation of the water level of saltwater is an important metric of wetland HR to sea level rise. This study improves the methodology of quantifying wetland hydrologic resilience at a regional scale, representing an important first step towards understanding the wetland hydrological and ecological resilience to future intensified climate disturbances in coastal regions and beyond.